International multicenter survey on screening and confirmatory testing in primary aldosteronism

Abstract

Objective Primary aldosteronism (PA) is one of the most frequent causes of secondary hypertension. Although clinical practice guidelines recommend a diagnostic process, details of the steps remain incompletely standardized. Design and Methods In the present SCOT-PA survey, we have investigated the diversity of approaches utilized for each diagnostic step in different expert centers through a survey using Google questionnaires. A total of 33 centers from 3 continents participated. Results We demonstrated a prominent diversity in the conditions of blood sampling, assay methods for aldosterone and renin, and the methods and diagnostic cut-off for screening and confirmatory tests. The most standard measures were modification of antihypertensive medication and sitting posture for blood sampling, measurement of plasma aldosterone concentration (PAC) and active renin concentration by chemiluminescence enzyme immunoassay, a combination of aldosterone to renin ratio with PAC as an index for screening, and saline infusion test (SIT) in a seated position for confirmatory testing. The cut-off values for screening and confirmatory testing showed significant variation among centers. Conclusions Diversity of the diagnostic steps may lead to an inconsistent diagnosis of PA among centers and limit comparison of evidence for PA between different centers. We expect the impact of this diversity to be most prominent in patients with mild PA. The survey raises two issues: the need for standardization of the diagnostic process and revisiting the concept of mild PA. Further standardization of the diagnostic process/criteria will improve the quality of evidence and management of patients with PA.

Aldosterone and renin concentrations and blood pressure in young Indigenous and non‐Indigenous adults in the Northern Territory: a cross‐sectional study

“…Some test centres deem an ARR value greater than 50 pmol/mU as a positive screening test result; 14 an ARR beyond this threshold was identified in eleven remote ABC participants (5%), sixteen urban ABC participants (32%), and 32 TEC participants (42%) (Box 1). Other test centres define a positive screening result as an elevated ARR (> 70 pmol/mU) together with plasma aldosterone concentration greater than 270 pmol/L; 13 these criteria were met by three remote ABC participants (1%), eleven urban ABC participants (22%), and fifteen TEC participants (20%).…”

“…ARR values exceeded 70 pmol/mU in about one‐quarter of TEC and urban ABC participants, but in only six people in the remote ABC group (3%). The proportion of positive primary aldosteronism screening test results would be higher were lower ARR thresholds applied (30 or 50 pmol/mU 13‐15 ). Systolic and diastolic blood pressure levels were higher for men, and increased with waist circumference and BMI in all three study groups; systolic blood pressure increased with ARR in the TEC but not the ABC group.…”

“…Further, confirmatory testing to establish primary aldosteronism diagnoses had not yet been undertaken, and its prevalence could consequently only be inferred. The prevalence of positive screening test results depends on its definition; the threshold we applied (70 pmol/mU) is typical for Australian practice, 13 and no minimum plasma aldosterone concentration was required; this relatively high threshold yields a conservative estimate of the number of participants with possible primary aldosteronism 30 . Finally, primary aldosteronism screening was not conducted according to the international Endocrine Society recommendations, 31 (ie, we screened all participants, not just those with higher blood pressure or resistant hypertension) as abnormal aldosterone regulation has been identified in some people without hypertension, 7,26,32 suggesting that its production can begin to rise prior to the onset of hypertension 6 …”

“…Direct renin concentration was reported in mU/L; the between‐run analytic coefficients of variation were 10.0% at 5.1 mU/L and 4.3% at 82.4 mU/L. The ARR was calculated by dividing plasma aldosterone concentration by direct renin concentration; an ARR exceeding 70 pmol/mU was deemed a positive screening test result for primary aldosteronism 13 …”

Prevalence of primary aldosteronism in acute stroke or transient ischemic attack: a systematic review and meta-analysis

“…However, only in the absence of medication interference, an ARR cut-off of >70 pmol/mU has a sensitivity and specificity greater than 95% ( 26 ). There is a paucity of data to provide any robust recommendation on ARR thresholds whilst on interfering medications ( 27 – 29 ).…”